Semiconductor packages are popularly used to house integrated circuits. Typical semiconductor packages include chip scale packages (CSPs) and ball grid arrays (BGAs). The semiconductor packages may include contacts to establish electrical connectivity between the integrated circuit and external components. For example, the semiconductor packages may include contact balls or bumps (e.g., solder bumps) to electrically and physically connect the semiconductor package to a printed circuit board (PCB). Typically, the contacts are electrically and physically mounted to copper pads on the PCB. PCBs with semiconductor packages tend to be included in electronic devices, such as mobile telephones and the like.
The contacts of conventional CSPs and BGAs are arranged in a symmetrical matrix. This is illustrated in FIG. 1, where a portion of a semiconductor package 100 having ball-type contacts 102 is illustrated. While there may be an occasional missing contact (e.g., designated by region 104) and/or rows and columns of contacts 102 may only be present at the periphery of the package 100 (e.g., a center region of the package does not have contacts such that the contacts generally form a square or rectangle), the contacts 102 are arranged in a uniform pitch in an X direction and in a uniform pitch in a Y direction. The X and Y direction pitches are typically the same, but may differ. Industry standard pitches range from 0.4 millimeters (mm) to 0.8 mm, and 0.3 mm pitches have been proposed.
With additional reference to FIGS. 2 and 3, shown is a portion of the package 100 as mounted on a PCB 106 by connection of the contacts 102 to pads 108. The size of the pads 108 may range from about 230 micrometers (μm) to about 350 μm and may have a pitch that corresponds to the contacts (e.g., about 0.4 mm to about 0.8 mm). Conductive traces 110 on the surface of the PCB 106 or sandwiched between layers of the PCB 106 may connect the pads 108 to other components. The routing (also referred to as “fan out”) of the traces 110 is made in accordance with the location of the contacts 102 and pads 108. Conventional trace width and isolation of the traces 110 may range from about forty μm to about one hundred μm.
Contacts 102 may be used to couple the integrated circuit in the package 100 to other components so as to exchange signals. These contacts 102 may be referred to as input/output (I/O) contacts and are labeled I/O in the illustrated example. Other contacts 102 may be used to couple the integrated circuit in the package 100 to ground (e.g., ground contacts in the illustrated example are labeled GND), to power (e.g., power contact in the illustrated example are labeled Vcc), to a heat sink or heatslug (heatslug contacts are not shown in the illustrated example), or to some other point. Ground contacts, power contacts, and heatslug contacts are often placed in respective clusters that are internally connected in the package 100.